First second of vide is over exposed

[Peted]

Hi, I am doing a time lapse project with the PI, and would like to take 1 or 2 second videos every so often then join these to gather. So a typical time lapse but vids instead of stills.

The problem i have is the half first second of the video is always over exposed. it is like it take just under a second for the camera to calculate the exposure. So does any one know a way i can tell the camera to record for 3 seconds but only save the last 2 seconds or does any one no of a command line utility which can trim the first second off a h264 file?


Many thanks
Pete

[jamesh]

You are right in that there is a time taken to adjust the exposure. The trick would be to run raspivid in the mode that allows you to start and stop (effectively pause) the recording, even though the preview is still running - which is where the exposure is calculated. You can do this with the signal option which can pause/unpause the recording. You then write a small script with the timing loop in it that send the signal to the raspivid process to turn it on and off. Or I htin there is a timed option (or would be easy to add) that can take x seconds of video them pause for y seconds.

You'll get a single video - no need to stitch individual short segments together.

I cannot remember the exact options, but raspivid -? should bring them up.